1) Field of the Invention
The present invention relates to a display element and a method of manufacturing the display element, and more particularly, to an organic electroluminescence (EL) element and a method of manufacturing the EL element.
2) Description of the Related Art
An organic EL display using organic EL elements is currently in use. The organic EL display has a substrate made of a transparent material on an emission side and on a side opposite to the emission side of the display. Since each layer that constitutes the organic EL element is extremely thin, the substrate is provided to fix and reinforce each layer. Light from a light emitting unit in the organic EL element is transmitted through the substrate on the emission side of the organic EL display and emitted to the outside of the display. A portion of the light from the light emitting unit sometimes experiences a total reflection from a boundary of the substrate on the emission side and absorbed in the inside of the organic EL display. To avoid this, various technologies have been proposed to change an angle of the light from the light emitting unit in the organic EL display in such a manner that the light enters an output surface of the substrate at an angle equal to or smaller than a critical angle are proposed as described in, for example, Japanese Patent Application Laid-Open. No. 100189251, Japanese Patent Application Laid-Open No. 2001-332388, and Japanese Patent Application Laid-Open No. 2000-323272.
The technology disclosed in Japanese Patent Application Laid-Open No. 10-189251 and the technology disclosed in Japanese Patent Application Laid-Open No. 2001-332388 involve providing a reflection surface that reflects the light from the light emitting unit to change the angle of the light. It is very difficult to provide a structure having only a reflection surface without providing a substrate or the like on the emission side of the light emitting unit. Therefore, it is conceivable to provide the reflection surface on the emission side substrate at a position corresponding to a periphery of the light emitting unit. In the configuration in which the reflection surface is provided on the substrate at a position corresponding to a periphery of the light emitting unit, a portion of the light from the light emitting unit totally reflects from the output surface of the substrate and enters the reflection surface provided in a periphery of a light emitting unit in another pixel. The light that enters the reflection surface of another pixel is considered to reflect from the reflection surface and an electrode in the light emitting unit and allowed to emit from the output surface of the substrate.
However, when light supplied from a light emitting unit of one pixel enters a reflection surface provided corresponding to another pixel, so-called a crosstalk in which light of a different pixel is emitted may occur. The crosstalk may lead to deteriorations of image quality such as blurring of the contour of an image and recognition of a ghost image that cannot be displayed. The technology disclosed in Japanese Patent Application Laid-Open No. 2003-323272 involves providing a diffuser on the emission side of the substrate. Even when a diffuser is provided, crosstalk may occur similarly to the technologies described in Japanese Patent Application Laid-Open No. 10-189251 and Japanese Patent Application Laid-Open No. 2001-332388. As a result, it is necessary to prevent the deterioration of image quality in displays including organic EL displays from occurring in order to emit light from the light emitting unit efficiently.
The organic EL display may have a reduced contrast due to illumination in the room or outside light such as solar radiation. In the case of organic EL displays with a reflection electrode in the light emitting unit, the outside light that enters the light emitting unit from the observer side reflects from the reflection electrode, so that the outside light together with display light travels to the observer side, thereby causing a reduction in contrast. To reduce such a reduction in contrast, a technology involving using a low reflection electrode made of a low reflective material in the light emitting unit of the organic EL display is conceived. Provision of a low reflective electrode in the light emitting unit leads to a reduction in reflection toward the observer side of the outside light that enters the light emitting unit to minimize a reduction in contrast.
The technology disclosed in Japanese Patent Application Laid-Open No. 10-189251 involves providing a reflection surface in the periphery of the light emitting unit. To change the angle of light from the light emitting unit and minimizing the reduction in contrast simultaneously, it may be considered sufficient to provide a reflection surface in the periphery of the light emitting unit and a low reflection electrode in the light emitting unit. However, when the reflection surface is provided in the periphery of the light emitting unit, the outside light that enters the reflection surface may be reflected directly in the direction of the observer side. The outside light that travels from the reflection surface in the direction of the observer without entering the low reflection electrode may be considered to be a cause of a reduction in contrast. The outside light may travel in the direction of the observer side after being reflected between the reflection surfaces as well as traveling as it is in the direction of the observer side after entering the reflection surface. Thus, when a reflection surface and a low reflection electrode are provided parallelly, the outside light may be returned in the direction of the observer without entering the low reflection electrode.
The present invention has been made in light of the problems and it is an object of the present invention to provide a display capable of minimizing a reduction in image quality in emitting light from the light emitting unit and a method of manufacturing the display.